Friday, October 30, 2015

I'm skeptical that a 700-year-old mito genome can be used as evidence of prehistoric population movements. Obviously, for that sort of thing we'd need a sequence from before recorded history. Nevertheless, the discovery of mtDNA haplogroup U5a2a in the Eastern Pamirs is still very interesting.

The complete mitochondrial genome of one 700-year-old individual found in Tashkurgan, Xinjiang was target enriched and sequenced in order to shed light on the population history of Tashkurgan and determine the phylogenetic relationship of haplogroup U5a. The ancient sample was assigned to a subclade of haplogroup U5a2a1, which is defined by two rare and stable transversions at 16114A and 13928C. Phylogenetic analysis shows a distribution pattern for U5a2a that is indicative of an origin in the Volga–Ural region and exhibits a clear eastward geographical expansion that correlates with the pastoral culture also entering the Eurasian steppe. The haplogroup U5a2a present in the ancient Tashkurgan individual reveals prehistoric migration in the East Pamir by pastoralists. This study shows that studying an ancient mitochondrial genome is a useful approach for studying the evolutionary process and population history of Eastern Pamir.

The presence of Indian-specific mtDNA haplogroup M52 is surprising. Maykop territory was located just south of the steppe, but M52 isn't found in any of the Bronze and Iron Age samples from the steppe tested to date.

Here's the comment from Haak, from an abstract titled The role of the Caucasus in the formation of the Eurasia's genetic makeup: Insights and questions from ancient DNA research.

Recent genetic research on autosomal and uniparentally-inherited markers has shown a remarkable genetic uniformity of Caucasian populations despite the region’s notable linguistic and cultural diversity. When compared to neighbouring regions, the smooth genetic transition from the Near/Middle East to the Caucasus is in stark contrast to the marked differences to populations from the East European steppes. Flanked by the Black and the Caspian Seas, it remains unclear to what extent the Caucasus served as a corridor and whether and if so when ancient migrations had affected and shaped the region’s genetic profile. Ancient DNA research on Mesolithic, Neolithic and Bronze Age individuals from Western Eurasia have recently thrown fresh light on the Caucasus as region, which appears to have played a critical role in the formation of the genetic ancestry of the Yamnaya people, Bronze Age pastoralist of the east European steppes. The Yamnaya carry strong signals of eastern hunter-gatherer (EHG) ancestry and ancient Near Eastern ancestry that is different from the one that giving rise to early European farmers. While modern-day Armenians are the best proxy for the putative source population of the EHG dilution in the steppes, it is highly likely that prehistoric cultural groups from the Caucasus will provide a much better temporal and contextual fit.

Actually, I'd say western Georgians are the best proxy for the putative source population of the EHG dilution in the steppes. See here...

Wednesday, October 28, 2015

Determining the timing, identity and direction of migrations in the Mediterranean Basin, the role of “migratory routes” in and among regions of Africa, Europe and Asia, and the effects of sex-specific behaviors of population movements have important implications for our understanding of the present human genetic diversity. A crucial component of the Mediterranean world is its westernmost region. Clear features of transcontinental ancient contacts between North African and Iberian populations surrounding the maritime region of Gibraltar Strait have been identified from archeological data. The attempt to discern origin and dates of migration between close geographically related regions has been a challenge in the field of uniparental-based population genetics. Mitochondrial DNA (mtDNA) studies have been focused on surveying the H1, H3 and V lineages when trying to ascertain north-south migrations, and U6 and L in the opposite direction, assuming that those lineages are good proxies for the ancestry of each side of the Mediterranean. To this end, in the present work we have screened entire mtDNA sequences belonging to U6, M1 and L haplogroups in Andalusians—from Huelva and Granada provinces—and Moroccan Berbers. We present here pioneer data and interpretations on the role of NW Africa and the Iberian Peninsula regarding the time of origin, number of founders and expansion directions of these specific markers. The estimated entrance of the North African U6 lineages into Iberia at 10 ky correlates well with other L African clades, indicating that U6 and some L lineages moved together from Africa to Iberia in the Early Holocene. Still, founder analysis highlights that the high sharing of lineages between North Africa and Iberia results from a complex process continued through time, impairing simplistic interpretations. In particular, our work supports the existence of an ancient, frequently denied, bridge connecting the Maghreb and Andalusia.

We report sequencing-based whole-genome association analyses to evaluate the impact of rare and founder variants on stature in 6,307 individuals on the island of Sardinia. We identify two variants with large effects. One variant, which introduces a stop codon in the GHR gene, is relatively frequent in Sardinia (0.87% versus <0.01% elsewhere) and in the homozygous state causes Laron syndrome involving short stature. We find that this variant reduces height in heterozygotes by an average of 4.2 cm (−0.64 s.d.). The other variant, in the imprinted KCNQ1 gene (minor allele frequency (MAF) = 7.7% in Sardinia versus <1% elsewhere) reduces height by an average of 1.83 cm (−0.31 s.d.) when maternally inherited. Additionally, polygenic scores indicate that known height-decreasing alleles are at systematically higher frequencies in Sardinians than would be expected by genetic drift. The findings are consistent with selection for shorter stature in Sardinia and a suggestive human example of the proposed 'island effect' reducing the size of large mammals.

We report ~17.6 million genetic variants from whole-genome sequencing of 2,120 Sardinians; 22% are absent from previous sequencing-based compilations and are enriched for predicted functional consequences. Furthermore, ~76,000 variants common in our sample (frequency >5%) are rare elsewhere (<0.5% in the 1000 Genomes Project). We assessed the impact of these variants on circulating lipid levels and five inflammatory biomarkers. We observe 14 signals, including 2 major new loci, for lipid levels and 19 signals, including 2 new loci, for inflammatory markers. The new associations would have been missed in analyses based on 1000 Genomes Project data, underlining the advantages of large-scale sequencing in this founder population.

Monday, October 26, 2015

Various genetic data (classic markers, mitochondrial DNAs, Y chromosomes and genome-wide single-nucleotide polymorphisms (SNPs)) have confirmed the coexistence of three major human populations on the Japanese Archipelago: Ainu in Hokkaido, Ryukyuans in the Southern Islands and Mainland Japanese. We compared genome-wide SNP data of the Ainu, Ryukyuans and Mainland Japanese, and found the following results: (1) the Ainu are genetically different from Mainland Japanese living in Tohoku, the northern part of Honshu Island; (2) using Ainu as descendants of the Jomon people and continental Asians (Han Chinese, Koreans) as descendants of Yayoi people, the proportion of Jomon genetic component in Mainland Japanese was ~18% and ~28% in Ryukyuans; (3) the time since admixture for Mainland Japanese ranged from 55 to 58 generations ago, and 43 to 44 generations ago for the Ryukyuans, depending on the number of Ainu individuals with varying rates of recent admixture with Mainland Japanese; (4) estimated haplotypes of some Ainu individuals suggested relatively long-term admixture with Mainland Japanese; and (5) highly differentiated genomic regions between Ainu and Mainland Japanese included EDAR and COL7A1 gene regions, which were shown to influence macroscopic phenotypes. These results clearly demonstrate the unique status of the Ainu and Ryukyuan people within East Asia.

Despite recent advances in population genomics, much remains to be elucidated with regard to East Asian population history. The Ainu, a hunter-gatherer population of northern Japan and Sakhalin island of Russia, are thought to be key to elucidating the prehistory of Japan and the peopling of East Asia. Here, we study the genetic relationship of the Ainu with other East Asian and Siberian populations outside the Japanese archipelago using genome-wide genotyping data. We find that the Ainu represent a deep branch of East Asian diversity more basal than all present-day East Asian farmers. However, we did not find a genetic connection between the Ainu and populations of the Tibetan plateau, rejecting their long-held hypothetical connection based on Y chromosome data. Unlike all other East Asian populations investigated, the Ainu have a closer genetic relationship with northeast Siberians than with central Siberians, suggesting ancient connections among populations around the sea of Okhotsk. We also detect a recent genetic contribution of the Ainu to nearby populations, but no evidence for reciprocal recent gene flow is observed. Whole genome sequencing of contemporary and ancient Ainu individuals will be helpful to understand the details of the deep history of East Asians.

Background: Domestication of the now-extinct wild aurochs, Bos primigenius, gave rise to the two major domestic extant cattle taxa, B. taurus and B. indicus. While previous genetic studies have shed some light on the evolutionary relationships between European aurochs and modern cattle, important questions remain unanswered, including the phylogenetic status of aurochs, whether gene flow from aurochs into early domestic populations occurred, and which genomic regions were subject to selection processes during and after domestication. Here, we address these questions using whole-genome sequencing data generated from an approximately 6,750-year-old British aurochs bone and genome sequence data from 81 additional cattle plus genome-wide single nucleotide polymorphism data from a diverse panel of 1,225 modern animals.

Results: Phylogenomic analyses place the aurochs as a distinct outgroup to the domestic B. taurus lineage, supporting the predominant Near Eastern origin of European cattle. Conversely, traditional British and Irish breeds share more genetic variants with this aurochs specimen than other European populations, supporting localized gene flow from aurochs into the ancestors of modern British and Irish cattle, perhaps through purposeful restocking by early herders in Britain. Finally, the functions of genes showing evidence for positive selection in B. taurus are enriched for neurobiology, growth, metabolism and immunobiology, suggesting that these biological processes have been important in the domestication of cattle.

Conclusions: This work provides important new information regarding the origins and functional evolution of modern cattle, revealing that the interface between early European domestic populations and wild aurochs was significantly more complex than previously thought.

Thursday, October 22, 2015

Summary: The bacteria Yersinia pestis is the etiological agent of plague and has caused human pandemics with millions of deaths in historic times. How and when it originated remains contentious. Here, we report the oldest direct evidence of Yersinia pestis identified by ancient DNA in human teeth from Asia and Europe dating from 2,800 to 5,000 years ago. By sequencing the genomes, we find that these ancient plague strains are basal to all known Yersinia pestis. We find the origins of the Yersinia pestis lineage to be at least two times older than previous estimates. We also identify a temporal sequence of genetic changes that lead to increased virulence and the emergence of the bubonic plague. Our results show that plague infection was endemic in the human populations of Eurasia at least 3,000 years before any historical recordings of pandemics.

Study co-author Dr Marta Mirazón-Lahr, from Cambridge's Leverhulme Centre for Human Evolutionary Studies (LCHES), points out that a study earlier this year from Willerslev's Copenhagen group showed the Bronze Age to be a highly active migratory period, which could have led to the spread of pneumonic plague.

"The Bronze Age was a period of major metal weapon production, and it is thought increased warfare, which is compatible with emerging evidence of large population movements at the time. If pneumonic plague was carried as part of these migrations, it would have had devastating effects on small groups they encountered," she said.

"Well-documented cases have shown the pneumonic plague's chain of infection can go from a single hunter or herder to ravaging an entire community in two to three days."

Monday, October 19, 2015

A new preprint on the genetic history of North Eurasia has just appeared at bioRxiv. Here's the abstract:

Siberia and Western Russia are home to over 40 culturally and linguistically diverse indigenous ethnic groups. Yet, genetic variation of peoples from this region is largely uncharacterized. We present whole-genome sequencing data from 28 individuals belonging to 14 distinct indigenous populations from that region. We combine these datasets with additional 32 modern-day and 15 ancient human genomes to build and compare autosomal, Y-DNA and mtDNA trees. Our results provide new links between modern and ancient inhabitants of Eurasia. Siberians share 38% of ancestry with descendants of the 45,000-year-old Ust-Ishim people, who were previously believed to have no modern-day descendants. Western Siberians trace 57% of their ancestry to the Ancient North Eurasians, represented by the 24,000-year-old Siberian Malta boy. In addition, Siberians admixtures are present in lineages represented by Eastern European hunter-gatherers from Samara, Karelia, Hungary and Sweden (from 8,000-6,600 years ago), as well as Yamnaya culture people (5,300-4,700 years ago) and modern-day northeastern Europeans. These results provide new evidence of ancient gene flow from Siberia into Europe.

My initial thought was that the MA1 or Mal'ta boy-related admixture estimate of 57% for Western Siberians (in fact, Mansis) was way too high. However, I checked it using qpAdm and the Mansis from the Human Origins dataset, and apparently it does make sense as a three-way model including MA1, Han Chinese and Georgians. The full qpAdm output is available here.

Mansi
Han 0.367
MA1 0.561
Georgian 0.073

chisq 0.278, tail prob 0.870155

Curiously, I get a very similar result with Eastern European hunter-gatherers (EHG) in place of MA1, and the fit is almost as good. The full output is here.

Mansi
Han 0.402
EHG 0.537
Georgian 0.061

chisq 0.916, tail prob 0.632459

In any case, we can safely assume that Mansis harbor a lot of MA1/EHG-related ancestry. Perhaps as much as ~60%. However, I have to say that this quote from the paper makes no sense whatsoever:

Our findings also point to Western Siberians Mansi as a likely source of the ANE [aka MA1-related] ancestry among northeastern Europeans.

Really? Mansis? Not even proto-Mansis, or some sort of Mansi-related population?

Also, as far as I can see, the authors consider Y-haplogroup N1c1 as an EHG paternal marker, simply because they dated its main expansion to 7,100-4,900 BP based on present-day samples. Please note that Karelia_HG and Samara_HG are classified as EHG.

The Western Siberian admixture into the Eastern Europeans likely began before the Yamnaya culture period (5.3-4.7 kya), since the admixtures with Mansi are also very strong among hunter gatherers from Northeastern Europe from 6.6-8 kya (Karelia HG, Samara HG and to lesser degree Motala HG and Hungary Gamba HG; Fig. S21f-q) that predated the Yamnaya people. Therefore Western Siberian admixtures into northeastern Europe likely began prior to 6,600 years ago, coinciding with the expansion of Y-DNA haplogroup N1c1 among Siberians and northeastern Europeans (7,100-4,900 years ago). Since haplogroup N likely originates in Asia or Siberia, its presence among eastern Europeans likely reflects ancient gene flows from Siberia into Eastern Europe.

The problem is that this isn't yet supported by any direct evidence from ancient DNA. Thus far, we know that EHG carried Y-haplogroups J, R1a and R1b, but no N1c1. Later populations, with significant EHG ancestry, such as Corded Ware, Khvalynsk and Yamnaya, carried mostly R1a and R1b, as well as I2a and Q1a, but again, no N1c1.

That's not to say that N1c1 won't ever turn up in EHG remains. But in my opinion the major subclades of N1c1 can't be associated with EHG, but rather with later populations of more complex origin, such as early Uralic-speakers with significant levels of East Eurasian admixture.

By the way, the claims about Ust-Ishim in the paper are interesting, but in my opinion not very parsimonious based on the data we have at the moment. I could be wrong though. Let's wait and see.

Sunday, October 18, 2015

Iain Mathieson, a Harvard scientist and the lead author of a recent peprint on the history of natural selection in Europe, has a website where he occasionally posts articles. He recently posted a review on the origins and spread of lactase persistence (LP) in Europe. He ends the review with the following comment:

This is actually rather consistent with the Itan et al. result, and it seems plausible to me that the [European LP] allele first appeared in Central Europe, was spread around Europe by the LBK, before being introduced to the steppe later by migration from Europe.

I can imagine that this conclusion won't be everyone's cup of tea, but I'd say it's a reasonable one for the time being.

Also, it's interesting to see the presence of the European LP allele in the Srubnaya Culture remains from the Middle Bronze Age Caspian steppe.

We didn’t find any evidence for LP in early farming populations like the LBK, or in early Bronze age steppe populations like the Yamnaya. In as-yet unreported data, we find a few copies of the allele in the Srubnaya - a later steppe population who seem to have some European Farmer-like ancestry.

The same Srubnaya sample also shows a high ratio of Y-haplogroup R1a-Z93 (4/6), which is today one of the most common Y-haplogroups in South Asia.

Now, the LP allele in South Asia is the same one as in Europe. So what this suggests is that at some point, probably during the later stages of the Bronze Age, steppe nomads closely related to the Srubnaya people moved into South Asia, bringing with them both R1a-Z93 and the European LP allele.

I'm pretty sure we'll be hearing more on that soon from the good people at Broad MIT/Harvard.

Friday, October 16, 2015

I thought I'd revisit the issue of Basque origins with my new Principal Component Analysis (PCA) of West Eurasia. The useful thing about this PCA is that it gets around two problems that routinely affect PCA featuring ancient samples: projection bias, otherwise known as shrinkage, and exaggerated outcomes for individuals with high counts of homozygous genotypes.

A couple of recent papers argued that Basques were the direct descendants of local hunter-gatherers and early Neolithic farmers who arrived in Iberia from the eastern Mediterranean. This is probably correct for the most part, but it doesn't tell the whole story.

On the PCA above, Basques are quite distinct from Early Neolithic, Middle Neolithic and Copper Age Iberians (marked Iberia_EN, Iberia_MN and Iberia_CA, respectively), because they are significantly more eastern. In fact, they cluster with the only Bronze Age Iberian on the plot (Iberia_BA), which is the same individual that I found to harbor steppe-related ancestry (see here).

Thus, the story told by the PCA is that Basques are the progeny of Bronze Age Iberians, who, unlike their Copper Age predecessors, experienced a pulse of steppe-related admixture from the east.

However, the statistic f4(Basque, Iberia_Chalcolithic; Yamnaya_Samara,Chimp)=0.00168 is significantly positive (Z=8.1), as is the statistic f4(Spanish, Iberia_Chalcolithic; Yamnaya_Samara, Chimp)= 0.00092 (Z=4.6). This indicates that steppe ancestry occurs in present-day southwestern European populations, and that even the Basques cannot be considered as mixtures of early farmers and hunter-gatherers without it (4).

The key question now is who brought the steppe-related ancestry to Basque country. Were they Indo-Europeans or speakers of Proto-Basque? Also, did they actually come from the steppe, or somewhere nearby, like the Carpathian Basin?

The reason I mention the Carpathian Basin is because, as per the PCA, Basques more or less cluster between Copper Age Iberians and some of the Bronze Age Hungarians (marked Hungary_BA). But this is just one possibility, and I'm not sure at this stage how plausible it looks with, say, formal statistics.

Tuesday, October 13, 2015

From now on, every time a new dataset of ancient West Eurasian samples is made available online, I'll run it like this.

Please note that the plots above include the majority of recently published ancient samples, and yet they are not affected by projection bias, otherwise known as shrinkage. If you're confused by some of the acronyms in the PCA key, see here.

Saturday, October 10, 2015

Open access at bioRxiv. Lots of new samples in this one. The Principal Component Analysis (PCA) below from the paper appears to be affected by projection bias or shrinkage, but it's more or less correct. Can't wait to get my hands on the genotype data.

Abstract: The arrival of farming in Europe around 8,500 years ago necessitated adaptation to new environments, pathogens, diets, and social organizations. While indirect evidence of adaptation can be detected in patterns of genetic variation in present-day people, ancient DNA makes it possible to witness selection directly by analyzing samples from populations before, during and after adaptation events. Here we report the first genome-wide scan for selection using ancient DNA, capitalizing on the largest genome-wide dataset yet assembled: 230 West Eurasians dating to between 6500 and 1000 BCE, including 163 with newly reported data. The new samples include the first genome-wide data from the Anatolian Neolithic culture, who we show were members of the population that was the source of Europe's first farmers, and whose genetic material we extracted by focusing on the DNA-rich petrous bone. We identify genome-wide significant signatures of selection at loci associated with diet, pigmentation and immunity, and two independent episodes of selection on height.

Tweets from ASHG 2015 can be found here. By the way, I know that today at 5.15pm, Baltimore time, Razib will be at Iosif Lazaridis' ASHG talk on the genetic affinities of Neolithic Anatolians. If his tweets don't appear there, you'll find them here.

Update: Here are some of those tweets from Razib...

@iosif_lazaridis revision of paper @mathiesoniain with more ancestry stuff on biorxiv soon [in fact, see here]

Thursday, October 8, 2015

By recent I mean post-Neolithic, because this genome is only dated to ~4,500 BP. Admittedly though, I am skeptical that all of the Eurasian admixture arrived so late, and await more data points from prehistoric Africa. By the way, this individual belongs to Y-haplogroup E1b1 and mtDNA haplogroup L3. The main text is behind a pay wall, but the supp info is free:

Characterizing genetic diversity in Africa is a crucial step for most analyses reconstructing the evolutionary history of anatomically modern humans. However, historic migrations from Eurasia into Africa have affected many contemporary populations, confounding inferences. Here, we present a 12.5x coverage ancient genome of an Ethiopian male (‘Mota’) who lived approximately 4,500 years ago. We use this genome to demonstrate that the Eurasian backflow into Africa came from a population closely related to Early Neolithic farmers, who had colonized Europe 4,000 years earlier. The extent of this backflow was much greater than previously reported, reaching all the way to Central, West and Southern Africa, affecting even populations such as Yoruba and Mbuti, previously thought to be relatively unadmixed, who harbor 6-7% Eurasian ancestry.

The results presented in the Report “Ancient Ethiopian genome reveals extensive Eurasian admixture throughout the African continent“ were affected by a bioinformatics error. A script necessary to convert the input produced by samtools v0.1.19 to be compatible with PLINK was not run when merging the ancient genome, Mota, with the contemporary populations SNP panel, leading to homozygote positions to the human reference genome being dropped as missing data (the analysis of admixture with Neanderthals and Denisovans was not affected). When those positions were included, 255,922 SNP out of 256,540 from the contemporary reference panel could be called in Mota. The conclusion of a large migration into East Africa from Western Eurasia, and more precisely from a source genetically close to the early Neolithic farmers, is not affected. However, the geographic extent of the genetic impact of this migration was overestimated: the Western Eurasian backflow mostly affected East Africa and only a few Sub-Saharan populations; the Yoruba and Mbuti do not show higher levels of Western Eurasian ancestry compared to Mota.
We thank Pontus Skoglund and David Reich for letting us know about this problem.

Sunday, October 4, 2015

I've made a discovery. The Near Eastern-related ancestors of the Yamnaya steppe pastoralists were also the ancestors of present-day Georgian Mingrelians, or their very close relatives, and in all likelihood speakers of Kartvelian, which has a long history in the Caucasus. Here's a nice map from Wikipedia and a pic of some Mingrelians. Check out the impressive headware.

TreeMix is very specific and precise about this. In my analyses, based on a couple of different methods, the Mingrelians are the only population chosen as a source for the Near Eastern-related ancestry in the Yamnaya.

Keep in mind, this is an unsupervised test and the algorithm has an infinite number of choices, because migration edges can run from any part of the tree, and yet it chooses the Mingrelians. By the way, if anyone's wondering, I did also try the Bronze Age Armenians, to no avail.

This outcome is also more or less reproducible with more complex topologies that include samples from Central Asia. In the graph below the Georgian Mingrelians form a clade with the Near Eastern-related ancestry of the Yamnaya. It'd be interesting to see if other Georgian groups, like the Svans, do even better, if that's actually possible, but they're not available at the moment.

I actually came up with basically the same result earlier this year using qpAdm (see here). But at the time I was skeptical of its usefulness because qpAdm only offers a supervised test, so picking Georgians as a reference population and getting a good statistical fit doesn't mean as much as a reproducible unsupervised migration edge.

Now, judging by their ADMIXTURE results, these Georgian Mingrelians do carry some Early European farmer-related ancestry, which is missing in the Yamnaya (see here). Therefore, it's likely that ancient samples from the west or northwest Caucasus will prove to be even better proxies for the Near Eastern-related ancestry in the Yamnaya.

The samples used to produce the above TreeMix graphs are listed here. They're sourced from the Allentoft et al., Haak et al., and Lazaridis et al. datasets. I limited the markers to ~65K transversion (high confidence) SNPs that overlap between these datasets.

When different Indo-European speaking groups settled Europe, they did not arrive in terra nullius. Both from the perspective of the Anatolian hypothesis and the Steppe hypothesis the carriers of Indo-European speech likely encountered existing populations that spoke dissimilar, unrelated languages. Relatively little is known about the Pre-Indo-European linguistic landscape of Europe, as the Indo-Europeanization of the continent caused a largely unrecorded, massive linguistic extinction event. However, when the different Indo-European groups entered Europe, they incorporated lexical material from Europe’s original languages into their own vocabularies. By integrating these “natural samples” of Pre-Indo-European speech, the original European linguistic and cultural landscape can partly be reconstructed and matched against the Anatolia and the Steppe hypotheses. My results reveal that Pre-Indo-European speech contains a clear Neolithic signature emanating from the Aegean, and thus patterns with the prehistoric migration of Europe’s first farming populations. These results also imply that Indo-European speech came to Europe following a later migration wave, and therefore favor the Steppe Hypothesis as a likely scenario for the spread of the Proto-Indo-Europeans.

Also, we've known for a while now that the good people at Broad MIT/Harvard have analyzed remains from Neolithic Anatolia, but it's nice to see this framed in the context of the Indo-European homeland debate.

Close genetic relationship of Neolithic Anatolians to early European farmers

Iosif Lazaridis et al.

We study 1.2 million genome-wide single nucleotide polymorphisms on a sample of 26 Neolithic individuals (~6,300 years BCE) from northwestern Anatolia. Our analysis reveals a homogeneous population that was genetically similar to early farmers from Europe (FST=0.004±0.0003 and frequency of 60% of Y-chromosome haplogroup G2a). We model Early Neolithic farmers from central Europe and Iberia as a genetic mixture of ~90% Anatolians and ~10% European hunter-gatherers, suggesting little influence by Mesolithic Europeans prior to the dispersal of European farmers into the interior of the continent. Neolithic Anatolians differ from all present-day populations of western Asia, suggesting genetic changes have occurred in parts of this region since the Neolithic period. We suggest that the language spoken by the homogeneous Anatolian-European Neolithic farmers is unlikely to have been the same as that spoken by the Yamnaya steppe pastoralists whose ancestry was derived from eastern Europe and a different population from the Caucasus/Near East [Haak et al. 2015], and discuss implications for alternative models of Indo-European dispersals.

Indeed, my view is that the implications of this data for the Anatolian hypothesis are fatal (see here). It might also have dire implications for the Armenian Plateau hypothesis, although for the time being this hypothesis limps on.

Feel free to post and discuss your favorite abstracts in the comments below. If anyone reading is going to this thing, I'd love to hear more about the Y-haplogroups of the Anatolian farmers.

Friday, October 2, 2015

To help things run more smoothly in the comments, I urge everyone taking part in the debates here about the colonization of the Eurasian steppe and the Indo-European homeland question to read carefully the following three papers. They're all open access:

In particular, please note the latest calibrated radiocarbon-based dates of the main archaeological cultures being discussed:

- Khvalynsk, Eneolithic, 4300–3800 cal BC

- Steppe Maikop, Early Bronze Age, 3800–3000 cal BC

- Yamnaya, Early Bronze Age, 3000–2450 cal BC

- Afanasievo, Early Bronze Age, 2900-2500 cal BC

- Early Catacomb, Early Bronze Age, 2600–2350 cal BC

Of course, Yamnaya are in large part of Eastern European hunter-gatherer (EHG) origin but with roughly 50% of Near Eastern-related ancestry from an unknown population (Haak et al. 2015). Paper #2 linked to above provides tentative isotopic evidence that the latter might be the Steppe Maikop people or their descendants (see paragraph 4 on page 58).

However, the Khvalynsk population from the Samara region harbors around 25% of the same or very similar Near Eastern-related ancestry (unpublished data courtesy of David Anthony). And, as per the dates above, Khvalynsk existed before Steppe Maikop.

Thus, although the increase of the Near Eastern-related ancestry on the steppe from the Khvalynsk to the Yamnaya periods can be tentatively attributed to Maikop influence, this cannot be the initial source of this type of ancestry on the steppe.

Moreover, dates older than 3,000 cal BC for Afanasievo appear to be spurious (see paper #3 above). If so, what this means is that Afanasievo is around the same age as Yamnaya, or perhaps a little younger, and thus the generally accepted hypothesis that Afanasievo derives from Yamnaya or pre-Yamnaya looks safe.

Now, it's especially important that everyone concerned is aware of the key climatic shifts on the steppe, because climatic changes are often invoked as likely causes of major population movements within and out of the steppe. So I'm re-posting here Table 1 from paper #1 (click to enlarge).

I'll update this post as new information comes in, which will hopefully be very soon. There are signals that something big is on the way from the Reich Lab pertaining to the Indo-European homeland debate (for instance, see here).

Thursday, October 1, 2015

The Afanasievo and Yamnaya samples published to date are remarkably homogeneous. Hopefully the bar graphs below, based on a couple of my recent ADMIXTURE runs, illustrate this well enough.

The Near Eastern-related ancestry proportions among the Yamnaya individuals do appear to rise steadily from early Yamnaya to late Yamnaya/early Catacomb. But the ancestral components remain the same, and if the increase in the Near Eastern-related admixture is real, the process is very subtle.

What this suggests to me is that groups of a southern provenance - in all likelihood Neolithic farmers seeking new land - arrived somewhere on the Pontic-Caspian steppe very early, perhaps even during the Early Neolithic, to eventually blend with local foragers. That's because the basic Yamnaya genotype had to have existed before the Yamnaya or pre-Yamnaya ancestors of the Afanasievo nomads set off on their 2000 km trek to the Minusinsk Basin in South Siberia, probably around 3,300 BC.

No doubt, the mixing didn't stop after the initial farmer/forger admixture event, and this is probably why the Near Eastern-related ancestry proportions rise gradually throughout the Yamnaya period. Indeed, considering the high mobility of Bronze Age steppe pastoralists, it's likely that long distance trade, alliances and marriages resulted in the genetic homogenization of vast stretches of Eastern Europe during their reign.